|Sam Jones Wednesday February
San Francisco has realised that where there's muck there's gas. The dog-loving city has decided to convert the 6,500 tonnes of faeces produced each year by its canine population into energy.
Within the next few months, Norcal Waste, a company that collects the city's rubbish, will begin a pilot programme which uses biodegradable bags and carts to gather droppings at a popular dog park.
The waste will be put in a methane digester, a tank in which bacteria feed on faeces for weeks to create methane gas. This can then be piped directly to gas stoves, heaters, turbines, or anything else powered by natural gas. It can also be used to generate electricity.
| San Francisco is ideally suited to the project as
animal faeces account for nearly 4% of its residential waste, nearly as
much as disposable nappies. It is also home to 240,000 dogs and cats. San
Franciscans recycle more than 60% of their rubbish.
Will Brinton, a Maine-based recycling consultant, said: "San Francisco is probably the king of pet cities. This could be very important to them."
Methane digesters are nothing new. More than 600 farm-based digesters have sprung up in Europe since the technology took off 20 years ago, and the machines are increasingly popular in dairy, chicken and pig farms across the US.
However, Norcal Waste is thought to be the first US company to use the digesters to convert pet waste to energy.
Some experts believe methane digestion must become more attractive economically before it gets popular. Landfill space is relatively cheap, and natural gas and electricity are still fairly inexpensive.